The storyline was a good one when all the pieces finally came together in the end. However, a book should be good all over and not just at the end. The author didn't really let the reader inside the characters' heads. And, to me, that's what makes Torchwood good. In fact, the characters were barely recognizable as Torchwood characters other than names and basic facts (Ianto makes coffee, Owen is a doctor, etc.) Also, there was an awful lot of bantering dialogue that tried to incorporate inside-joke-type lingo that just doesn't exist in any of the Torchwood episodes or other books.
I did, however, like that the book gave a clearer picture of what Cardiff is in relation to the universe by introducing the concept of "border princes". It sort of sounds as if Cardiff has (to borrow from another sci-fi program) its own "stargate" which is what they've been calling a "rift". Interesting concept.
The baffling thing about this novel in the beginning is the introduction of a character named James that just pops into Torchwood out of nowhere. No, you're not going crazy. Yes, he's supposed to be there. And that's all I have to say without giving it away.